In response to localized temperature increases, worker bees shield the comb from the external heat source by positioning themselves on the hot interior region of the hive's walls. Heat shielding reduces the transfer of heat from outside to inside the hive (Starks and Gilley, 1999) http://beheco.oxfordjournals.org/content/16/1/128.full

Bees also use their bodies as insulation to control hive temperature in summer.